This is interesting. What controls the methanol flow though, isn't it the BMS Solenoid? I think there must be a specific part in the system that failed to allow this to happen. Would be nice if Shiv or Mike could chime in.

I'm concerned because I am running the same system among probably hundreds of other people and I will have to upgrade parts or change things prior to Vargas stage 2.

I've never heard of this type of a failure before. Both the pump and solenoid would need to get stuck on to allow meth to spray off-boost and they run on independent circuits on the FSB unless it's one of the really old ones. Might be worth OP sending the FSB in to have that tested to determine if it failed and why.

I've never thought about it before but I suppose any meth kit electronics could get stuck on with the right kind of a failure. The best way to protect against it would be with a physical boost switch as an override. Like a circuit breaker if you will. Unless boost is over say 6psi the meth pump can't power on. Does the Aquamist controller use a physical boost line for reference?